7,631 research outputs found

### Modified tetrahedron equation and related 3D integrable models,II

This work is a continuation of paper (hep-th/9407146) where the Boltzmann
weights for the N-state integrable spin model on the cubic lattice has been
obtained only numerically. In this paper we present the analytical formulae for
this model in a particular case. Here the Boltzmann weights depend on six free
parameters including the elliptic modulus. The obtained solution allows to
construct a two-parametric family of the commuting two-layer transfer matrices.
Presented model is expected to be simpler for a further investigation in
comparison with a more general model mentioned above.Comment: 17 pages,LaTeX fil

### Factorization of the finite temperature correlation functions of the XXZ chain in a magnetic field

We present a conjecture for the density matrix of a finite segment of the XXZ
chain coupled to a heat bath and to a constant longitudinal magnetic field. It
states that the inhomogeneous density matrix, conceived as a map which
associates with every local operator its thermal expectation value, can be
written as the trace of the exponential of an operator constructed from
weighted traces of the elements of certain monodromy matrices related to $U_q
(\hat{\mathfrak{sl}}_2)$ and only two transcendental functions pertaining to
the one-point function and the neighbour correlators, respectively. Our
conjecture implies that all static correlation functions of the XXZ chain are
polynomials in these two functions and their derivatives with coefficients of
purely algebraic origin.Comment: 35 page

### Quantum model of interacting ``strings'' on the square lattice

The model which is the generalization of the one-dimensional XY-spin chain
for the case of the two-dimensional square lattice is considered. The subspace
of the ``string'' states is studied. The solution to the eigenvalue problem is
obtained for the single ``string'' in cases of the ``string'' with fixed ends
and ``string'' of types (1,1) and (1,2) living on the torus. The latter case
has the features of a self-interacting system and looks not to be integrable
while the previous two cases are equivalent to the free-fermion model.Comment: LaTeX, 33 pages, 16 figure

### Connecting lattice and relativistic models via conformal field theory

We consider the quantum group invariant XXZ-model. In infrared limit it
describes Conformal Field Theory with modified energy-momentum tensor. The
correlation functions are related to solutions of level -4 of qKZ equations. We
describe these solutions relating them to level 0 solutions. We further
consider general matrix elements (form factors) containing local operators and
asymptotic states. We explain that the formulae for solutions of qKZ equations
suggest a decomposition of these matrix elements with respect to states of
corresponding Conformal Field Theory .Comment: 22 pages, 1 figur

### Exact evaluation of density matrix elements for the Heisenberg chain

We have obtained all the density matrix elements on six lattice sites for the
spin-1/2 Heisenberg chain via the algebraic method based on the quantum
Knizhnik-Zamolodchikov equations. Several interesting correlation functions,
such as chiral correlation functions, dimer-dimer correlation functions, etc...
have been analytically evaluated. Furthermore we have calculated all the
eigenvalues of the density matrix and analyze the eigenvalue-distribution. As a
result the exact von Neumann entropy for the reduced density matrix on six
lattice sites has been obtained.Comment: 33 pages, 4 eps figures, 3 author

### Modified Tetrahedron Equations and Related 3D Integrable Models

Using a modified version of the tetrahedron equations we construct a new
family of $N$-state three-dimensional integrable models with commuting
two-layer transfer-matrices. We investigate a particular class of solutions to
these equations and parameterize them in terms of elliptic functions. The
corresponding models contain one free parameter $k$ -- an elliptic modulus.Comment: 26 pages, LaTeX fil

### Fifth-neighbor spin-spin correlator for the anti-ferromagnetic Heisenberg chain

We study the generating function of the spin-spin correlation functions in
the ground state of the anti-ferromagnetic spin-1/2 Heisenberg chain without
magnetic field. We have found its fundamental functional relations from those
for general correlation functions, which originate in the quantum
Knizhink-Zamolodchikov equation. Using these relations, we have calculated the
explicit form of the generating functions up to n=6. Accordingly we could
obtain the spin-spin correlator up to k=5.Comment: 10 page

### Branching Fraction Measurements of the SM Higgs with a Mass of 160 GeV at Future Linear \ee Colliders

Assuming an integrated luminosity of 500 fb$^{-1}$ and a center-of-mass
energy of 350 GeV, we examine the prospects for measuring branching fractions
of a Standard Model-like Higgs boson with a mass of 160 GeV at the future
linear \ee collider TESLA when the Higgs is produced via the Higgsstrahlung
mechanism, \ee \pfr HZ. We study in detail the precisions achievable for the
branching fractions of the Higgs into WW$^*$, ZZ$^*$ and \bb. However, the
measurement of BF(H \pfr \gaga) remains a great challence. Combined with the
expected error for the inclusive Higgsstrahlung production rate the uncertainty
for the total width of the Higgs is estimated.Comment: 17 pages Latex, including 7 figure

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